Photographic elements, compositions and processes

ABSTRACT

N-hydroxyurea silver halide developing agents in photographic compositions, elements and processes provide desired developing activity. These can be employed in various photographic products including photosensitive compositions, photographic elements and chemical transfer systems. They can be used in combination with other silver halide developing agents and with addenda commonly employed in photographic elements.

United States Patent [191 Wilson et a1.

PHOTOGRAPHIC ELEMENTS, COMPOSITIONS AND PROCESSES Inventors: Burton D. Wilson; Paul E.

Woodgate, both of Rochester; Richard W. Henn, Pittsford, all of NY.

Assignee: Eastman Kodak Company, Rochester, NY.

Filed: July 3, 1974 Appl. No.: 485,405

Related U.S. Application Data Continuation-impart of Ser, No. 252,036, May 10, 1972,

U.S. Cl 96/95; 96/66 R; 96/76 R;

96/1 14.1 Int. Cl. G030 1/06; G03c 1/02 Field of Search 96/95, 76 R, 50 R, 66,

References Cited UNITED STATES PATENTS 2/1939 Holt 96/66 R Primary Examiner-Mary F. Kelley Attorney, Agent, or FirmR. E. Knapp [57] ABSTRACT N-hydroxyurea silver halide developing agents in photographic compositions, elements and processes pro vide desired developing activity. These can be employed in various photographic products including photosensitive compositions, photographic elements and chemical transfer systems. They can be used in combination with other silver halide developing agents and with addenda commonly employed in photographic elements.

25 Claims, No Drawings PHOTOGRAPHIC ELEMENTS, COMPOSITIONS AND PROCESSES This is a continuation-in-part application of U.S. patent application Ser. No. 252,036 of Wilson, Woodgate and Henn, filed May 10, 1972.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to N-hydroxyurea reducing agents in photographic elements. compositions and processes. In one of its aspects it relates to photographic compositions containing these N-hydroxyurea reducing agents. In another aspect it relates to photographic elements containing such reducing agents. in a further aspect it relates to photographic compositions and to processes, such as processing with heat, to develop an image in a photographic element.

2. Description of the State of the Art The use of various nitrogen containing compounds as photographic developing agents and for other purposes in photographic materials is known. For example, hydroxylamines have been used as developing agents as described, for example, in Belgian Pat. No, 558,501 of Gevaert published July 15, 1957; U.S. Pat. No. 3,287,125 ofGreen et al, issued Nov. 22, 1966 and the like. Certain urea derivatives have also been employed in photographic materials as described in Canadian Patent 456,029 and US. Pat. No. 2,404,774 of Derisch et al.', U.S. Pat. No. 2,477,323 of Wood issued July 26, 1949 and US. Pat. No. 2,819,165 of Mackey, issued Jan. 7, 1958. Hydroxylmethylurea compounds have also been employed in diazo materials as described in US. Pat. No. 3,453,112 of Schaefer, issued July 1, 1969; U.S. Pat. No. 3,316,092 of Klimkowski et al., issued April 25, 1967 and French Pat. No. of addition 83,978 of Bauchet published Sept. 28, 1964. However, these are not N-hydroxyurea reducing agents of the invention. There has been a continuing need to provide nitrogen containing reducing agents for photosensitive materials which provide reduced staining propensity. While hydroxylamine and various derivatives have been employed for this purpose, they have not always provided sufficient developing activity or stability. This is demonstrated in following comparative Example 9.

There has also been a continuing need to provide combinations of reducing agents which provide reduced processing time and reduced staining propensity. This is especially important in photosensitive materials for processing with heat in which the processing agents remain in the photosensitive material after processing. Photosensitive materials for processing with heat are well known, as described, for example, in U.S. Pat. No. 3,457,075 of Morgan et al., issued July 22. 1969; U.S. Pat, No. 3,152,904 of Shepard et al., issued Oct. 13, 1964; US Pat. No. 3,392,020 of Yutzy and Yackel, issued July 9, 1968; U.S. Pat. No. 3,782,941 of Hartman et al., issued Jan 1, 1974; and U.S. Pat. No. 3,801,321 of Evans et al., issued Apr. 2, 1974.

It is an object of the invention to provide photographic elements, compositions and processes, such as photographic materials for processing with heat, containing certain silver halide developing agents which provide decreased processing time with reduced staining propensity.

SUMMARY OF THE lNVENTlON According to this invention decreased processing time with reduced staining propensity, without significant loss of desired sensitometric properties, is provided in a photographic element, composition, and process by an N-hydroxyurea silver halide developing agent. Such N-hydroxyurea silver halide developing agents provide especially useful results when employed in combination with other silver halide developing agents, such as 3-pyrazolidone silver halide developing agents.

The described N-hydroxyurea silver halide developing agents are useful in photothermographic materials containing a photosensitive component, such as photosensitive silver halide, with an oxidation-reduction image-forming combination.

The N-hydroxyurea silver halide developing agents described yield colorless oxidation products which are useful in photosensitive materials which require that the processing agents remain in the photosensitive material after processing. The N-hydroxyurea developing agents provide surprisingly reduced propensity for staining compared to prior art silver halide developing agents such as hydroquinone and para-aminophenol silver halide developing agents which provide undesired oxidation stain. This is demonstrated in following comparative Example 17.

Detailed Description of the Invention A variety of N-hydroxyurea reducing agents are useful according to the invention. One test for useful N- hydroxyurea reducing agents when the reducing agent is to be employed in a photothermographic material is set out in following Example 18.

A useful class of N-hydroxyurea silver halide developing agents according to the invention is represented by the formula:

wherein R, R and R are hydrogen, alkyl, especially alkyl containing 1 to 4 carbon atoms, such as methyl, ethyl, propyl and butyl, or aryl, typically aryl containing 6 to 10 carbon atoms, such as phenyl, tolyl and xylyl. R, R and/or R can contain substituent groups which neither adversely affect developing activity of the described N-hydroxyurea silver halide developing agents nor adversely affect the sensitometric properties of photosensitive elements or compositions containing the N-hydroxyurea developing agent. Such substituent groups include, for example, halogen or amino groups. Within the described class of N-hydroxyurea silver halide developing agents especially useful reducing agents are those wherein R is hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms, such as phenyl, tolyl or xylyl; R is hydrogen, alkyl of l to 4 carbon atoms or aryl containing 6 to 10 carbon atoms such as phenyl, tolyl or xylyl; R is hydrogen, alkyl containing 1 to 4 carbon atoms or phenyl, tolyl or xylyl. Examples of useful N-hydroxyurea silver halide developing agents are compounds wherein R, R and R in the described structure are as follows:

Compound No. R

Especially useful N-hydroxyurea silver halide developing agents are represented by the formula:

wherein R is phenyl, p-methylphenyl, methoxyphenyl or p-chlorophenyl.

The described N-hydroxyurea reducing agents can be prepared by procedures known in the art.

The described N-hydroxyurea reducing agents can be employed in a range of physical locations in a photo graphic system. They can be employed in one or more layers of a photographic element and/or in a processing composition if desired. The optimum location will depend upon the desired image, processing conditions, particular photographic system and the like. For example, the described N-hydroxyurea silver halide developing agents can be employed in a processing composition, such as an aqueous, alkaline developer solution and they can be incorporated into one or more layers of a photographic element, such as a photographic silver halide emulsion layer, a layer between the support and a photographic silver halide emulsion layer, and/or an overcoat layer.

Various development activators can be employed in the practice of the invention to activate the described N-hydroxyurea developing agents. These include any of those which provide the desired activation of the described developing agents. These include, for instance, alkaline development activators, such as inorganic alkalies including, for example, sodium hydroxide, potassium hydroxide and/or lithium hydroxide, alkali metal carbonates such as sodium carbonate, and potassium carbonate, alkali metal phosphates such as trisodium phosphate, and/or organic alkaline development activators such as quaternary ammonium bases, amines such as amino alkanols and similar alkaline materials and/or alkali releasing materials. The described development activators can be employed in a processing composition and/or applied to the described photographic element in any suitable manner including, for example, dipping, spraying and/or suitable surface applications such as with rollers or other mechanical means.

The pH of the processing composition should be sufficient to provide desired activation of the described developing agent. A pH of about to about 14 is typically employed.

A wide range of concentration of the described developing agent is useful not only in a photosensitive composition or element but also in a processing composition in the practice of the invention depending sired upon the desired image, the developing agent employed, processing conditions and the like. A concentration of about 0.5 to about 50 grams, and typically about 2 to about 20 grams of developing agent is suitable per liter of processing composition.

The described silver halide developing agents are useful in combination with any silver halide developing agent or developing agent precursor which does not adversely affect the developing activity of the N- hydroxyurea compounds. Silver halide developing agents which are useful with the described N- hydroxyurea developing agents include, for example, polyhydroxybenzenes, such as hydroquinone silver halide developing agents, such as hydroquinone, alkylsubstituted hydroquinones, as exemplified by tertiary butyl hydroquinone, methylhydroquinone, 2,5-dimethylhydroquinore and 2,6-dimethylhydroquinone; catechols and pyrogallol; chloro-substituted hydroquinones, such as chlorohydroquinone or dichlorohydroquinone; alkoxy substituted hydroquinones such as methoxy hydroquinone or ethoxy hydroquinone; aminophenol developing agents such as 2,4- diaminophenols and methylaminophenols; ascorbic acid developing agents such as ascorbic acid, ascorbic acid ketals and ascorbic acid derivatives; hydroxylamine developing agents such as N,N-di(2-ethoxyethyl)hydroxylamine; 3-pyrazolidone developing agents such as l-phenyl-3-pyrazolidone and/or 4- methyl-4-hydroxymethyll -phenyl-3-pyrazolidone', sulfonamidophenol developing agents, such as described in U.S. Pat. No. 3,782,941 of Hartman et al., issued Jan. I, 1974, and the like. Combinations of these developing agents can be employed if desired.

The combination of the described N-hydroxyurea silver halide developing agents with a 3-pyrazolidone developing agent provides surprisingly reduced processing time to provide desired image density without undeincrease in minimum density. Typical 3- pyrazolidone silver halide developing agents which can be employed in this combination are described, for example, in U.S. Pat. No. 3,453,109 of Lee, issued July I, 1969; U.S. Pat. No. 3,284,200 of Ficken, issued Nov. 8, 1966; U.S. Pat. No. 3,523,795 of Ohkubo et a1., issued Aug. ll, 1970; British Pat. No. 1,093,281 issued Nov. 29, 1967 and U.S. Pat. No. 2,875,048 of Haist and King, issued Feb. 24, 1959. Typical 3-pyrazolidone silver halide developing agents which can be employed in the described combination include, for example, 1- phenyl-4,4-dihydroxymethyl-3-pyrazolidone; l-phenyl- 4-methyl-4-hydroxymethyl-3-pyrazolidone; l-phenyl- 3-pyrazolidone; 5-phenyl-3-pyrazolidone; 5-methyl 3- pyrazolidone and the like.

A range of concentrations of the described N- hydroxyurea silver halide developing agent can be employed with a range of concentrations of the described 3-pyrazolidone silver halide developing agents. Typically a concentration ratio of 10 parts by weight N- hydroxyurea silver halide developing agent is employed for each part by weight of 3-pyrazolidone silver halide developing agent. A typical concentration range of 3- pyrazolidone silver halide developing agent in a processing composition is about 0.05 grams to about 5 grams of 3-pyrazolidone silver halide developing agent per liter of processing composition.

The described silver halide developing agents can be employed in a range of photographic processing compositions, such as in photographic silver halide developer compositions, hardener compositions, monobaths, and the like.

The photographic processing composition can contain a silver halide solvent if desired. Typical silver halide solvents include. for example, alkali metal or ammonium thiosulfates and thiocyanates, such as sodium thiosulfate, sodium thiocyanate or ammonium thiocyanate and organic silver halide solvents such as thiourea and certain organic amines.

The processing composition as described can be a monobath. Typical components of monobaths are described, for example, in the Monobath Manual" by Grant Haist. published by London Press. 1966.

One embodiment of the invention is a photosensitive composition comprising a photosensitive silver salt and an N hydroxyurea silver halide developing agent as described, The photosensitive silver salt is typically a photosensitive silver halide.

A range of concentration of the described N- hydroxyurea silver halide developing agent is useful in a photographic element and/or photosensitive composition such as a photosensitive silver halide emulsion. Typically the concentration of silver halide developing agent is about 0.1 mole to about 50 moles of developing agent per mole of silver present in the photographic element or photosensitive composition, preferably about 0.5 moles to about 4 moles of silver halide developing agent per mole of silver in the element or composition. This typically corresponds to about to about 500 milligrams of silver halide developing agent per 929 square centimeters of support. When used in photosensitive materials for processing with heat typically a concentration of about 01 to about 2 moles of N- hydroxyurea developing agent is employed per mole of silver in the photosensitive material.

Silver halide materials which are useful according to the invention include any photosensitive silver halide, such as silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. The silver halide materials which are suitable are described in the Product Licensing Index, Volume 92, December, l97l, publication 9232, pages 107-1 l0 in paragraphs 1, H and Ill. A photosensitive silver halide can be chemically sensitized as described in paragraph ll] of this Product Licensing Index publication.

The silver halide photosensitive elements and compositions according to the invention can contain development modifiers, antifoggants, stabilizers, hardeners, plasticizers and lubricants, coating aids, matting agents, brighteners and spectral sensitizing dyes described in the product Licensing Index, Vol. 92, December, 197 l publication 9232, pages l07-l 10. The silver halide photosensitive compositions according to the invention can be chemically sensitized. washed and/or coated employing the procedures described in this publication.

Another embodiment of the invention is a photosensitive silver halide emulsion comprising photosensitive silver halide, a binder and an N-hydroxyurea silver haiide developing agent as described.

A photographic element and/or composition as described can contain various colloids alone or in combination as vehicles, binding agents and in various layers. Typically hydrophilic materials are useful in those instances where aqueous solutions are to be used in processing. However, in those instances in which the photosensitive material is for processing with heat, a hydrophobic binder can be useful. Accordingly, hydrophilic and/or hydrophobic materials can be employed as binders depending on the particular photosensitive material and the intended processing. Suitable hydrophilic materials include naturallyoccurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water soluble polyvinyl compounds like poly (vinylpyrrolidone), acrylic polymers and the like. Other synthetic polymeric compounds which are useful include dispersed vinyl compounds such as in latex form and particularly those which provide increased dimensional stability of photographic materials. Suitable synthetic polymers include those described in the Product Licensing Index, Volume 92, December, 1971, publication 9232, pages l07l 10 in paragraph VIII.

The photosensitive and/or other layers of a photographic element according to the invention can be coated on a wide variety of supports. Typical supports include cellulose ester film, poly(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resinous materials as well as glass, paper, metal and the like. Typically a flexible support is employed, especially a paper support which can be partially acetylated or coated with baryta and/or an alpha olefin polymer particularly a polymer of an alpha olefin containing 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene-butene copolymers and the like.

Another embodiment of the invention is a photographic element comprising a support having thereon a photosensitive silver salt, typically photosensitive silver halide, an N-hydroxyurea silver halide developing agent, as described, and a binder.

The photosensitive silver halide materials employed according to the invention can be x-ray or other nonspectrally sensitized materials or they can contain spectral sensitizing dyes as described.

The sensitizing dyes and/or other addenda, such as the described silver halide developing agents according to the invention, can be added from water solutions or suitable organic solvent solutions can be used. The compounds can be added using various procedures known in the photographic art as described in the mentioned Product Licensing Index publication.

The described N-hydroxyurea silver halide developing agents can be employed in combination with a stabilizer or so called stabilizer precursor. These stabilizer precursors are typically sulfur-containing compounds, contiguous to photographic silver halide, which in the presence of an activator and/or heat, breakdown or cleave to form a compound that combines or complexes with the silver halide in unexposed and undeveloped areas of a photographic element to form a complex or compound which is believed to be a silver mercaptide which is more stable than silver halide to light humidity and ambient conditions. Such compounds are described, for example, in US. Pat. No. 3,301,678 of Humphlett et al., issued Jan. 3 l 1967; Belgian Pat. No. 709,967 and Belgian Patent 709,900. Examples of useful silver halide stabilizer precursors include 3-S- isothiuronium propane sulfonate', 2-S-isothiuronium ethane sulfonate and l,8-(3,6-dioxaoctane)bis(isothiuronium trichloroacetate). A suitable concentration of stabilizer precursor will vary depending on the particular photographic element, the desired image, processing conditions and the like. Other useful classes of stabilizers or stabilizer precursors are described, for example, in U.S. Pat. No. 3,707,377 of Tiers et al., issued Dec. 26, 1972. Usually a concentration of about 0.25 to about 10 moles of stabilizer precursor per mole of photosensitive silver halide in the element is suitable.

After exposure, the resulting latent image in a photographic element containing the described N hydroxyurea silver halide developing agent can be developed by contacting the element with an alkaline development activator as described. An especially useful activator is an alkaline aqueous solution containing an alkali metal hydroxide at a pH of about 10 to about 14.5, especially 12 to 14.5. The described development activators can be applied to the photographic element according to the invention in any suitable manner which provides desired activation including, for example, clipping, spraying, and/or surface application such as with rollers or by surface application processing.

So-called web processing can be employed as described, for example. in U.S. Pat. No. 3,179,517 ofTregillus et al., issued Apr. 20, 1965 or so-called stabilization processing as described in Russell et al., PSA Journal, Volume 168, Aug, 1950.

The time for processing a photographic element containing a developing agent according to the invention, that is developing a desired latent image, can vary over a wide range, typically between about 1 second to sev eral minutes depending on the desired image, processing conditions, particular developing agent and the like.

Processing conditions can also vary. When the described developing agent is in a processing solution and in a photographic element, processing is usually carried out under ambient pressures and temperatures of about C. to about C. If desired, higher temperatures can be used.

The described N-hydroxyurea silver halide developing agents can be employed in a diffusion transfer photographic system, especially a photographic silver salt diffusion transfer system. The described developing agents can be employed in one or more layers of a photographic element and/or in a processing composition in such a system if desired. Suitable diffusion transfer systems, processes, processing compositions and elements therefore are described, for example, in U.S. Pat. No. 2,452,181 of Land. issued Feb. 27, 1951; and U.S. Pat. No. 3,337,342 ofGreen, issued Aug. 27, 1967. Accordingly, another embodiment of the invention is: in a photographic product comprising in combination (a) a photographic element comprising photographic silver halide, (b) a processing composition containing a silver halide solvent. and (c) an image-receiving layer and N- hydroxyurea silver halide developing agent as described. The N-hydroxyurea silver halide developing agent is typically present in the processing composition. The product is typically employed for developing an image by exposing the photographic silver halide element to form a latent image therein; developing the latent image with a processing composition, such as at a pH of about 12 to about 14, containing the described N-hydroxyurea silver halide developing agent with a silver halide solvent; contacting undeveloped silver halide in the photographic silver halide layer with the sil ver halide solvent to form an imagewise distribution of a silver complex in the unexposed areas of the photographic silver halide layer; transferring atleast part of the silver complex to an image receiver layer contiguous to the photographic silver halide layer; reducing the silver complex in the presence of development nuclei to form a visible image in the receiver layer; and lowering the pH of the processing composition to below about 8 to form a stable developed image.

The developing agents according to the invention can be present in one or more layers of elements designed for color photography, for example, elements containing color-forming couplers, or elements to be developed in solutions containing color-forming couplers; or in so-ca1led false-sensitized color materials such as those described in U.S. Pat. No. 2,763,549 of Hanson, issued Sept. 18, 1956.

If desired, in addition to the described photosensitive compositions and elements the developing agents can be employed in so-called hardening developers such as described in U.S. Pat. No. 3,232,761 of Allen and Burness, issued Feb. 1, 1966; or in roller transport proces sors which is described in US. Pat. No. 3,025,779 of Russell et al., issued Mar. 20, 1962.

The described developing agents are also useful in photosensitive materials designed for processing with heat. Photosensitive materials for processing with heat in which the described N-hydroxyurea silver halide developing agents are useful are described, for example, in U.S. Pat. No. 3,457,075 of Morgan et al., issued July 22, 1969,- U.S. Pat. No. 3,152,904 of Sorenson et al., issued Oct. 13, 1964; U.S. Pat. No. 3,392,020 of Yutzy et al., issued July 9, 1968; Belgian Pat. No. 705,872 and U.S. Pat. No. 3,801,321 of Evans et al., issued Apr. 2, 1974. In photosensitive elements for processing with heat typically a support is provided having thereon an oxidation-reduction image forming combination comprising an oxidizing agent, typically a heavy metal salt oxidizing agent, such as a silver salt ofa fatty acid, with an N-hydroxyurea reducing agent and a catalyst for the image-forming combination, such as photosensitive silver halide. A visible image is produced after exposure of the photosensitive element within a short time, such as about 1 to about 60 seconds, after exposure by heating the element to moderately elevated temperatures, such as about C. to about C.

Accordingly, another embodiment of the invention in a photothermographic element comprising a support having thereon (a) a photosensitive silver salt, such as photosensitive silver halide, in association with (b) an oxidation-reduction image-forming combination comprising (i) an oxidizing agent, typically a heavy metal salt oxidizing agent, such as silver behenate, with (ii) an N-hydroxyurea reducing agent as described.

A typical concentration range of photosensitive silver salt, especially photosensitive silver halide, in the described photothermographic element is from about 0.005 to about 0.50 moles of photosensitive silver salt per mole of oxidizing agent.

It is believed that the latent image formed in the photographic silver salt upon imagewise exposure of the photothermographic material increases the reaction rate between the components of the photothermographic material upon heating the photothermographic material. It is believed that enables a lower processing temperature to be employed for developing an image which otherwise would not be possible. The terms photographic silver salt in association with and photographic silver halide in association with are intended to mean the photographic silver salt, such as photographic silver halide, is in a location with respect to the other described components of the photothermograhic material which enables this desired lower processing temperature and provides a more useful developed image.

In photothermographic materials the described N- hydroxyurea reducing agents can be employed in combin ation with other described reducing agents, typically substituted phenols and/or naphthols. For example, the N-hydroxyurea reducing agents can be employed in combination with bis-beta-naphthol reducing agents, such as 2,2'-dihydroxy-l,l binaphthol, 6,6'-dibromo- 2,2'-dihydroxy-l ,l '-binaphthol, 6,6'-dinitro-2,2'-dihydroxyl '-binaphthol, or bis-(Z-hydroxy-lnaphthoUmethane. and/or sulfonamidophenol reducing agents, such as described in U.S. Pat. No. 3,80l,321 of Evans. issued Apr. 2, 1974.

The oxidizing agent in the described oxidationreduction image-forming combination is typically a heavy metal salt oxidizing agent such as a silver salt oxidizing agent. The heavy metal salts of an organic acid are especially suitable. such as water insoluble silver salts of long-chain fatty acids which are substantially stable to light. Compounds which are silver salts of long-chain fatty acids include, for example, silver behenate, silver stearate, silver oleate, silver laurate, silver hydroxy stearate, silver caprate, silver myristate and silver palmitate. Oxidizing agents which are not silver salts of carboxylic acids can be employed if desired such as silver phthalazinone, silver benzotriazole and- /or silver saccharin. Oxidizing agents which are not silver salts can be employed if desired such as gold stearate, mercuric behenate, auric behenate and the like, but silver salts are preferred.

It is often desirable to employ a so-called activator toning agent in the photothermographic elements and compositions according to the invention in order to obtain improved tone and desired image density. The described activator toning agent is suitable in a range of concentration; however, it is especially suitable in a concentration of about 0.10 moles to about l.l moles of activator toning agent per mole of oxidizing agent employed such as per mole of silver behenate. A typical activator-toning agent is a cyclic imide such as phthalimide, N-hydroxyphthalimide, N-hydroxy-l ,8- naphthalimide, N-potassium phthalimide, N-silver phthalimide, N-mercury phthalimide, succinimide and- /or N-hydroxy succinimide. Other suitable activator toning agents include, for example, l-(2H)- phthalazinone, 2-acetyl phthalazinone and 2- phthalylphthalazinone.

Binders can be employed in the described photothermographic materials as described. Preferred binders are high molecular weight materials and resins including poly(vinyl butyral), cellulose acetate butyrate, polymethylmethacrylate, poly( vinyl pyrrolidone), ethyl cellulose, polystyrene, poly(vinyl chloride). chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloride-vinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and poly(vinyl alcohol).

If desired, the described photosensitive silver halide in the photothermographic material according to the invention can be prepared in situ. A method of preparing photosensitive silver halide in situ in a photothermographic material is described, for example, in U.S. Pat. No. 3.457.075 of Morgan et al., issued July 22, 1969.

In developing an image in a photothermographic material according to the invention a range of processing temperatures is suitable. The processing temperature range is typically about C. to about 250C. such as for about 1 to about 60 seconds. By increasing or decreasing the length of time of heating, a higher or lower temperature within the described range is useful.

Any suitable means is useful for providing the desired processing temperature range. The heating means can be a simple hot plate, roller or the like.

In some cases, if desired, a photothermographic element can be prepared wherein one or more components, such as the described photosensitive silver halide, can be in one layer and other components in other layers. For example, an element according to the invention can comprise a support, a layer containing photographic silver halide and a layer comprising the socalled oxidation-reduction image-forming combination comprising a heavy metal salt oxidizing agent as de scribed such as silver behenate with an N-hydroxyurea reducing agent as described.

A typical so-called oxidation-reduction imageforming combination according to the invention comprises silver behenate with the described N- hydroxyurea reducing agent and an activator toning agent which is typically phthalimide or l-(2H)- phthalazinone.

Other addenda known to be useful in photothermographic compositions and elements as described in British Pat. No. 1,161,777 published Aug. 20, 1969; U.S. Pat. No. 3,152,904 of Sorenson et al., issued Oct. l3, 1964; U.S. Pat. No. 3,457,075 of Morgan et al., issued July 22, 1969 and U.S. Pat. No. 3,801,32l of Evans et al., issued Apr. 2, 1974 can be employed in photothermographic materials according to the inventron.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 This example demonstrates reduced staining propensity of the N-hydroxyurea silver halide developing agents of the invention.

An alkaline solution of each of the N-hydroxyurea silver halide developing agents designated as compounds l-l l was permitted to evaporate to dryness in the presence of air. The residue in each instance was almost colorless.

The procedure was repeated with the exception that hydroquinone was employed in place of the N- hydroxyurea silver halide developing agent. The residue resulting upon evaporation was intensely colored.

This procedure was also repeated employing paraaminophenol in place of the described N- hydroxyurea silver halide developing agent. Upon evaporation the resulting residue was intensely colored.

This demonstrates that the N-hydroxyurea silver halide developing agents of the invention provide surprisingly reduced staining propensity compared to silver halide developing agents employed herefore.

EXAMPLES 2-9 This illustrates the use of N-hydroxyurea silver halide developing agents according to the invention in photosensitive materials for processing with heat.

A dispersion is prepared by mixing the following components:

Silver behenate 23.3 g Behenic acid 26.0 g Polyvinyl butyral 1.25 g Sodium bromide 1.31 g Acetonetoluene 1:1 parts by 500 ml volume] This mixture is ball-milled for 18 hours and the resulting dispersion is coated on a resin coated paper support at a wet thickness of 0.004 inches. The resulting coating is permitted to dry under atmospheric conditions. Various N-hydroxyurea reducing agents as indicated in following Table III are each dissolved in a mixture of alcohol and acetone and coated on separate pieces of the resulting photosensitive element. The N- hydroxyurea silver halide developing agent is present at a concentration of 0.02 mole of N-hydroxyurea silver halide developing agent per mole of total silver in the photothermographic element.

After the N-hydroxyurea reducing agent is introduced, the resulting photothermographic element is dried and exposed sensitometrically to light. The resulting image is developed by overall heating the photothermographic element on a heated metal plate at 140C. Images of moderate to high density are produced within about l to 3 seconds as indicated in following Table lll. Good density corresponds to 0.8 'max., Dense corresponds to 1.0 "max, Fair corresponds to 0.5 "max.

This is a comparative example.

The procedure set out in Example 2 was repeated with the exception that hydroxylamine sulfate was employed in place of the described N-hydroxyurea silver halide developing agent.

Upon exposure and overall heating, an image having almost no density was produced. The image density was very poor compared to the image density produced in each instance in Examples 2-9.

EXAMPLES 11-18 The procedure set out in Examples 2-9 was repeated with the exception that l-(2H )-phthalazinone in a concentration of 0.7 g/g Ag. was employed in the photothermographic elements described. In each instance, upon imagewise exposure to form a latent image followed by overall heating, an image was developed within about 2 to 4 seconds at a processing temperature of about 140C.

EXAMPLES 19-25 The procedure set out in Example 2 was repeated with the exception that l-( 2H)-phthalazinone was employed in the described photothermographic element in a concentration of 0.7 g/g Ag. Also the N- hydroxyurea reducing agents set out in Table IV were employed and the exposed photothermographic element was processed by overall heating at a temperature of 115C. or C. as described in Table IV.

The results in each instance are described in Table IV.

EXAMPLES 26-31 A photosensitive silver chloride gelatino emulsion was prepared containing 2.6 kilograms of gelatin and 2 moles of silver chloride. The silver chloride gelatino emulsion was mixed with 600 grams of gelatin, a wetting agent and one of the N-hydroxyurea silver halide developing agents as set out in following Table V. A concentration of 3.0 moles of N-hydroxyurea silver halide developing agent per mole of silver in the silver chloride gelatino emulsion was used.

The resulting silver chloride emulsion containing the N-hydroxyurea silver halide developing agent was coated on a paper support at a concentration of 0.04 grams of silver per 0.093 square meter of support. After drying, the photographic element was sensitometrically exposed to tungsten light. The resulting image was developed by immersing the photographic element in an aqueous sodium hydroxide solution containing 2.0 percent by weight sodium hydroxide for 5 seconds. An image was developed in each instance as set out in following Table V. In each instance very good image discrimination was produced.

Table V Incorporation in Silver Halide Photosensitive Emulsion The procedure set out in Example 26 was repeated with the exception that after sensitometric exposure the photographic element was heated for 10 seconds at 200C. A developed image was produced having moderate image density.

EXAMPLE 33 The procedure set out in Example 28 was repeated with the exception that after imagewise exposure the photographic element was heated for 10 seconds at 200C An image was developed having moderate density.

EXAMPLE 34 The procedure set out in Example 3l was repeated with the exception that after imagewise exposure the photographic element was heated for 10 seconds at 200C. A developed image resulted having moderate image density.

EXAMPLES 35-42 The procedure described in Examples 2-9 was repeated with the exception that l-( 2H J-phthalazinone in a concentration of 0.7 g per gram of silver and about 0.02 mole of p-benZene-sulfonamidophenol per mole of silver was employed in the photo-thermographic elements described. In each instance, upon imagewise exposure to form a latent image followed by overall heating, an image was developed within a few seconds at a processing temperature of about 140C.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is.

1. A photosensitive composition comprising a photosensitive silver salt and an N-hydroxyurea silver halide developing agent represented by the following formula:

v u I N-C-N wherein R is phenyl, p-methylphenyl, methoxyphenyl or p-chlorophenyl.

4. A photosensitive composition as in claim 1 also comprising a 3-pyrazolidone silver halide developing agent.

5. A photosensitive silver halide emulsion comprising photosensitive silver halide, a polymeric binder and an N-hydroxyurea silver halide developing agent represented by the following formula:

R OH

wherein R, R and R individually represent hydrogen, alkyl containing l to 4 carbon atoms or aryl containing 6 to l0 carbon atoms.

6. A photosensitive silver halide emulsion comprising photosensitive silver halide, a binder, an N- hydroxyurea silver halide developing agent and a sulfonamidophenol silver halide developing agent, said N- hydroxyurea silver halide developing agent being represented by the following formula:

wherein R, R, and R individually represent hydrogen. alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms.

7. A photographic element comprising a support having thereon a photosensitive silver salt, an N- hydroxyurea silver halide developing agent and a binder, said N-hydroxyurea silver halide developing agent being represented by the following formula:

R O R"I NC,-N

R2 OH wherein R, R and R individually represent hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms.

8. A photographic element as in claim 7 wherein said photosensitive silver salt is photographic silver halide. 9. A photographic element as in claim 7 wherein said Nhydroxyurea developing agent is represented by the formula:

wherein R, R, and R individually present hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms.

13. A photothermographic element as in claim 12 wherein said oxidizing agent is a heavy metal salt oxidizing agent.

wherein R is phenyl, p-methylphenyl, pmethoxyphenyl or p-chlorophenyl and (b) a polymeric binder.

18. A photothermographic composition comprising (a) photographic silver halide in association with (b) an oxidation-reduction image forming combination comprising (i) an oxidizing agent with (ii) an N- hydroxyurea reducing agent represented by the following formula:

wherein R R and R individually represent hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to l carbon atoms.

19. A photothermographic composition as in claim 18 also comprising a sulfonamidophenol silver halide reducing agent.

20. A photothermographic composition as in claim l6 18 also comprising a poly( vinyl butyral) binder.

21. A photothermographic composition as in claim 18 also comprising an activator-toning agent.

22. A photothermographic composition as in claim 12 also comprising an activator-toning agent which is l-( 2H)-phthalazinone or succinimide.

23. A photothermographic composition comprising (a) photosensitive silver halide in association with (b) an oxidation-reduction image-forming combination comprising (i) silver behenate with (ii) a reducing agent represented by the formula:

wherein R is phenyl. p-methylphenyl, pmethoxyphenyl o;- p-chlorophenyl and (b) a polymeric binder.

24. A method of developing an image in a photothermographic element comprising a support having thereon (a) photographic silver halide in association with (b) an oxidation-reduction image forming combination comprising (i) an oxidizing agent with (ii) an N hydroxyurea reducing agent and (c) a polymeric binder comprising heating said element to about C. to about 250C, said N-hydroxyurea reducing agent being represented by the following formula:

wherein R, R and R individually present hydrogen, alkyl containing 1 to 4 carbon atoms or aryl containing 6 to ID carbon atoms.

25. A method as in claim 24 comprising heating said photothermographic element to about 80C. to about 250C. for about 1 to about 60 seconds.

l i ii 

1. A PHOTOSENSITIVE COMPOSITION COMPRISING A PHOTOSENSITIVE SILVER SALT AND AN N-HYDROXYUREA SILVER HALIDE DEVELOPING AGENT REPRESENTED BY THE FOLLOWING FORMULA:
 2. A photosensitive composition as in claim 1 wherein said photosensitive silver salt is photosensitive silver halide.
 3. A photosensitive composition as in claim 1 wherein said N-hydroxyurea silver halide developing agent is represented by the formula:
 4. A photosensitive composition as in claim 1 also comprising a 3-pyrazolidone silver halide developing agent.
 5. A PHOTOSENSITIVE SILVER HALIDE EMULSION COMPRISING PHOTOSENSITIVE SILVER HALIDE, A POLYMERIC BINDER AND AN N-HYDROXYUREA SILVER HALIDE DEVELOPING AGENT REPRESENTED BY THE FOLLOWING FORMULA:
 6. A photosensitive silver halide emulsion comprising photosensitive silver halide, a binder, an N-hydroxyurea silver halide developing agent and a sulfonamidophenol silver halide developing agent, said N-hydroxyurea silver halide developing agent being represented by the following formula:
 7. A photographic element comprising a support having thereon a photosensitive silver salt, an N-hydroxyurea silver halide developing agent and a binder, said N-hydroxyurea silver halide developing agent being represented by the following formula:
 8. A photographic element as in claim 7 wherein said photosensitive silver salt is photographic silver halide.
 9. A photographic element as in claim 7 wherein said N-hydroxyurea developing agent is represented by the formula:
 10. A photographic element as in claim 7 also comprising a 3-pyrazolidone silver halide developing agent.
 11. A photographic element as in claim 7 also comprising a sulfonamidophenol silver halide developing agent.
 12. A PHOTOTHERMOGRAPHIC ELEMENT COMPRISING A SUPPORT HAVING THEREON (A) PHOTOGRAPHIC SILVER SALT IN ASSOCIATION WITH (B) AN OXIDATION-REDUCTION IMAGE-FORMING COMBINATION COMPRISING (I) AN OXIDIZING AGENT WITH (II) AN N-HYDROXYUREA REDUCING AGENT AND (C) A POLYMERIC BINDER, SAID N-HYDROXYUREA REDUCING AGENT BEING REPRESENTED Y THE FOLLOWING FORMULA:
 13. A photothermographic element as in claim 12 wherein said oxidizing agent is a heavy metal salt oxidizing agent.
 14. A photothermographic element as in claim 12 wherein said oxidizing agent is a silver salt of a long-chain fatty acid.
 15. A photothermographic element as in claim 12 also comprising an activator-toning agent.
 16. A photothermographic element as in claim 12 also comprising an activator-toning agent which is 1-(2H)-phthalazinone or succinimide.
 17. A photothermographic element comprising a support having thereon (a) photosensitive silver halide in association with (b) an oxidation-reduction image forming combination comprising (i) silver behenate with (ii) a reducing agent represented by the formula:
 18. A photothermographic composition comprising (a) photographic silver halide in association with (b) an oxidation-reduction image forming combination comprising (i) an oxidizing agent with (ii) an N-hydroxyurea reducing agent represented by the following formula:
 19. A photothermographic composition as in claim 18 also comprising a sulfonamidophenol silver halide reducing agent.
 20. A photothermographic composition as in claim 18 also comprising a poly(vinyl butyral) binder.
 21. A photothermographic composition as in claim 18 also comprising an activator-toning agent.
 22. A photothermographic composition as in claim 12 also comprising an activator-toning agent which is 1-(2H)-phthalazinone or succinimide.
 23. A photothermographic composition comprising (a) photosensitive silver halide in association with (b) an oxidation-reduction image-forming combination comprising (i) silver behenate with (ii) a reducing agent represented by the formula:
 24. A method of developing an image in a photothermographic element comprising a support having thereon (a) photographic silver halide in association with (b) an oxidation-reduction image forming combination comprising (i) an oxidizing agent with (ii) an N-hydroxyurea reducing agent and (c) a polymeric binder comprising heating said element to about 80*C. to about 250*C, said N-hydroxyurea reducing agent being represented by the following formula:
 25. A method as in claim 24 comprising heating said photothermographic element to about 80*C. to about 250*C. for about 1 to about 60 seconds. 